Every week, Tony Hetherington replies to readers' letters, adding comments, advice and the results of his enquiries. If you think you are a victim of financial mismanagement, or want advice before investing, write to Tony Hetherington, Financial Mail, 2 Derry Street, London W8 5TS. Sorry, but he cannot give personal replies. Please only send copies of original documents, which, we regret, cannot be returned.

JA writes: I received a phone call asking if I would be interested in selling my shares in Bionostics for £12 each. This would make me about £40,000, but I was told to keep the offer a secret and tell nobody, so I smelled a rat. Can you shed any light on this?

Congratulations on your sense of smell. You passed on to me the written confirmation of the offer. It came from Anderson & Collins, which claims to be an investment advice and management firm in Montreal.

It says it has a private client who wants to buy your shares in Bionostics, a health company with offices in Oxford and the US whose shares are traded in London.

So far, so good. But Bionostics shares have traded recently at about 28p, not £12, and the company has just agreed to a takeover bid from North Atlantic Value at 30p a share.

Finance director Kelly Winn told me Anderson & Collins had not been in touch about its curious client and his extravagant offer. 'I have never heard of them,' she said. 'If they are running through the shareholder register, they have not yet got to me.' So what are you to make of the mysterious approach from Anderson & Collins? Well, for a start, it is very hard to pin down this firm. It claims on its website to have been in business since 1983, yet the site itself was set up as recently as last August. The firm is not listed in the Montreal phone directory.

It is not licensed by investment regulators in the province of Quebec and inquiries in Montreal show that the address it uses is a private house.

The website does give one interesting clue, though. The billing contact for running the website is a Malaysian named Emil Yong.

And the same Mr Yong was behind the website for a similar company called Carlton Hedges.

Watchdogs in Jersey issued a public warning against this New York-based investment company last April, saying it was unlicensed.

Since then, a remarkable bit of work by the Economic Crime Department of the City of London Police led to the conviction in Hong Kong last Wednesday of a British fraudster named Everton Clive Davis.

Davis, 51, had been operating a bank account at HSBC in Hong Kong. About £200,000 went into the account from UK investors who, like you, had been phoned by people claiming to be from offshore investment firms, including Carlton Hedges.

Many police forces no longer have fraud squads, but the City Force has more than 150 officers devoted to combating this crime.

They got their opposite numbers in Hong Kong to arrest Davis when he tried to withdraw money from the HSBC account and at least half the cash has been recovered and will be returned to the UK victims.

If you had been taken in by Anderson & Collins it is likely you would have been asked for money up front, probably for a fake insurance policy that would supposedly guarantee you would hand over your shares once you were paid. And based on similar scams, your hefty premium would have been paid into a bank account in Hong Kong.

There never was any £40,000, and when the offer from Anderson & Collins collapsed, you would have been told your insurance premium of a few thousand pounds was not refundable.

Mrs GB writes: I took out car insurance last April through the Post Office, which was running a promotion offering £50 in postal orders as an incentive. However, I have still not received these and have written twice without reply. An email brought only an automated response, and when I phoned, I was kept on hold for so long that the line went dead. But before that happened I was told that there was an immense backlog of people all awaiting their postal orders.

I asked officials at the Post Office head office to investigate. They told me that one car in 50 is now insured by them, but they added: 'It is regrettable that in this particular instance we appear to have failed to meet our normally excellent quicker on standards of customer care.' The Post Office says almost 450,000 car owners took advantage of the £50 cashback offer and it denies that they were kept waiting.

A spokesman says: 'All our customers who bought a policy have had the promotional offer fulfilled and there were no general delays or backlogs in doing this.' Nonetheless, you have now been given a written apology, the £50 you had expected and an extra £50 to make up for the delay.

Abbey should be quicker on wills

RS writes: I have been left a large sum in my mother's will. The money is invested with Abbey and I am told that obtaining probate will take about three months, but that Abbey is notoriously slow in releasing funds and it could take a further three months. Abbey says no interest will be paid for the time from my mother's death to the release of the money. Is this legal?

Abbey has been having problems with wills. The bank says things started to go wrong late last year when more customers died than were expected and at the same time, key probate staff quit.

Since then, a number of changes have been made to try to speed things up, including giving branches power to handle some of the work. It should not take three months to release funds after the delivery of the Grant of Probate, so if this happens, contact me again.

Meanwhile, Abbey says interest will continue to be earned right up to the day you close your mother's account and by the time you read this you should have received an apology and a letter to this effect.

Why should I lose out because of tax error?

Mrs MIT writes: I received a PAYE coding notice that seemed much clearer than those sent in the past, so I wrote to Revenue & Customs to say that I thought I had been overtaxed in the past. As a result, I have since received cheques totalling £862 for tax overpaid between 2001 and 2007.

However, as I have been retired since 1995, I presume I have been overtaxed since then, not since 2001, but Revenue staff say they cannot look back more than six years. My modest income is from three different sources, but all are taxed under PAYE so I consider it to be the Revenue's fault that I have been overtaxed. Are you willing to contact them on my behalf?

I have contacted officials at the Revenue's head office and they have reopened your case. Legally, they were right to say that the law allows them to make repayments for only six years. However, when staff themselves have slipped up, they do have discretion to go back further and I am glad to say that they have now agreed to exercise this discretion in your favour.

One official told me: 'Mrs T has three PAYE sources of income and she overpaid tax because the codes we calculated for her did not use all of her allowances.' In cash terms, those unused allowances were worth £129 in total during the years from 1995 to 2000. The Revenue will add a further £28 in interest and a cheque for £157 should be arriving any day now.